I'm in the process of building a new detached garage, doing a good majority of the work myself. Garage is standing, and I'm starting to dot the I's and cross the T's on the electrical. I have a couple of questions if some of you don't mind chiming in with advice.

The garage sits ~80ft away from the main panel in the house. New wire capable of 200A service has been recently run to the house, but the box in the house is currently 100A. I intend to upgrade this panel after the garage is finished.

I'm looking to send 40-60A out to the garage. I've planned on having a sub box with at least 6 circuits available, two of them used for a 240V receptacle. the other 4 will be used for lighting, garage door opener, and receptacles for tools.

Q1: I've planned on running copper, 6/3-WG, to the garage underground in schedule 40. Adequate for my amperage needs? I've heard some say that due to the length I might need to go #4.

Q2: Some people have suggested aluminum would be cheaper, but a few electricians I've talked to (mostly retired guys) are insistent on NOT touching the stuff. Any thoughts on aluminum?

Q3: I can't seem to find a decent panel for the garage with a 40-60A main breaker. I intend on running from a double 40-60A breaker on the house box. I know that the garage requires a disconnect as well. Is it OK to have a 100A breaker at the garage box as long as the house breakers are 40-60A? Will the electrician doing my inspection freak over that, or is it common practice?

Q4: How many grounding rods should I sink at the garage? Dimensions are 20' x 30', it's been suggested to drop one near the box, and one at an opposing corner.

Thanks in advance to anyone who replies, apologies if I've botched any terminology.

HouseHelper

04-22-2011 12:30 PM

Q1 - Use #6 THHN/THWN for the two hots and neutral and #10 for the ground.
Q2 - There is no problem with using stranded Al wires. A 2-2-2-4 unsheathed cable (mobile home feeder) is readily available at home centers that will allow for up to a 90A feed.
Q3 - A 60A breaker at the main panel feeding a 100A disconnect at the subpanel is fine.
Q4 - Two ground rods, spaced a minimum of six feet apart. Drive in the first, lay the second down with the end against the first, mark the spot for the second at the other end... you are now eight feet apart.

italie

04-22-2011 01:46 PM

Quote:

Originally Posted by HouseHelper
(Post 634449)

Q1 - Use #6 THHN/THWN for the two hots and neutral and #10 for the ground.
Q2 - There is no problem with using stranded Al wires. A 2-2-2-4 unsheathed cable (mobile home feeder) is readily available at home centers that will allow for up to a 90A feed.
Q3 - A 60A breaker at the main panel feeding a 100A disconnect at the subpanel is fine.
Q4 - Two ground rods, spaced a minimum of six feet apart. Drive in the first, lay the second down with the end against the first, mark the spot for the second at the other end... you are now eight feet apart.

WOW, thank you for the blazing fast reply. Looks like I'm fairly on track as far as the original plan goes. A quick follow up question if you don't mind.

2-2-2-4 unsheathed is OK for underground distribution? Sorry if this is a blatantly obvious question, I've never used aluminum. If the price break isn't drastic I'll probably be sticking with copper, but still curious.

I should probably add that I'm in the Chicago area, everything will be in conduit. That information shouldn't matter much for the questions asked though.